It is common practice for cranes to be used to lift heavy objects in order to reposition them from one place to another. Known cranes come in various sizes and shapes and are designed to ensure the safe handling of a load while it is in transit. While it is always important that a crane operator be able to see the object he is lifting, depending on what is being lifted, and the purpose for the lift, a crane operator may need the ability to reposition himself vertically with respect to the object being lifted in order to ensure that the object is placed gently and safely in the desired location.
For example, a crane operator who is lifting debris left over from a demolition or construction project may safely operate a crane from a ground or near ground position as he most likely only needs to have enough visibility to see that the object being lifted does not impact anything as it is moved from one position to the next. This is especially true if the operator is handling debris as there is less concern about the integrity of the object being lifted as it is dropped in its new position. If however, the crane operator is operating an intermodal crane or other material handling machine that is lifting a container filled with finished goods that are to be shipped to a store or final customer, the operator may desire the ability to adjust his position to various eye levels with respect to the load so as to be able to see both above and below the load to, for example, look down over the side rail of a ship or on top of a rail car so as to be able to gently reposition the container in an exact spot.
In order to allow a crane operator to be able to adjust his position vertically with respect to a load, vertically-elevating operator cabs have been employed on cranes such as gantry cranes and the like. Traditionally, these vertically-elevating cabs have relied on lift systems comprised of wire ropes or chains to raise or lower the cab from one position to another. Various problems are associated with such lift systems including the fact that the ropes or chains may fray or break. Furthermore, such lift systems are rather complex and may not always prevent a repositioned cab from sliding back down toward the ground once it has been raised to a desired level. For these and various other reasons, a lifting system for a vertically-elevating cab used with a crane would be an important improvement in the art.